Method for resource allocation in a radio system

ABSTRACT

The present invention relates to a method for resource allocation in a radio system comprising base stations with respective coverage areas and mobile units. The interaction between the stations in the system is defined with the aid of measured and/or calculated field strengths from all base stations on relevant traffic routes in the geographic area of the radio system, preferably in the form of an exclusion matrix. An allocating matrix is formed by compressing the exclusion matrix by means of an allocating algorithm. The algorithm utilizes figures of merit which are on the one hand calculated by mathematical/logical means to form possible combinations of stations and utilizes on the other hand a random technique for selecting one of these combinations. The algorithm is iterated a number of times and different allocations are obtained thanks to the random technique. The best one of the allocations from any point of view is selected.

FIELD OF THE INVENTION

The present invention relates to a method for resource allocation in aradio system. Radio systems can be one-way with communication in onlyone direction, for example paging system, or two-way, for example mobileradio system. In the application, a mobile radio system is preferablydealt with, but it is understood that the invention is equally wellapplicable to one-way systems. It is important in a mobile radio systemthat accessible frequency resources are used in such a manner that thesystem capacity is optimized with the condition that the customersexperience an acceptable quality. In a microcell system in a denselypopulated area it is desirable that the channel allocation can betailored to the current traffic distribution. Such planning is a verydemanding task and there are great gains to be made if the systemoperator has full control over the inherent interferences in the system.Improved quality and traffic handling in a given frequency band is alsoequivalent to an increased frequency economy.

The following preconditions are given: a distribution of the trafficrequirement over, for example, Stockholm, system parameters which definewhich C/I (carrier to interference) interference characteristic isrequired for good reception and how much interference the receivertolerates in adjoining channels, and a frequency band of the system witha limited number of channels. It is the object to distribute thechannels to the different base stations in the given frequency range sothat the quality of the connection experienced by the customers meetsgiven minimum requirements.

STATE OF THE ART

The literature on the subject supplies information on how the problem issolved in principle. The method is as follows: a systematic descriptionis given of all restrictions which apply to channel allocation in theform of a so-called exclusion matrix. An exclusion matrix produces adescription in symbolic form of how different base stations,alternatively mobiles in different coverage areas, can be shared withrespect to co-channel and adjacent-channel conditions. Allocatingalgorithms are then used for finding exactly which channels thedifferent base stations must have for the minimum requirement forconnection quality to be met.

The exclusion matrix in turn enables an allocating program to be drivenand channel allocations are obtained for a situation with very wellknown and desired interference characteristics which ensure a goodconnection quality.

Much is written in the literature about algorithms for frequencyallocation (channel allocation) for telecommunication systems ofdifferent types. For example, William K. Hale mentions the followingprocedure which, simplified, consists of the following steps:

1. To define the current situation with a number of transmitters andtheir coverage area.

2. To number these transmitters.

3. To define in matrix form the relevant interaction between eachtransmitter and the coverage area of the other transmitters.

4. To carry out algebraic operations on rows in the matrix according toa predetermined scheme. In the same paper, this scheme constitutes theallocating algorithm.

5. The algorithm results in a changed matrix from which a channelallocation can be read out.

This procedure is deterministic which means that each time the algorithmis run through exactly the same allocation is obtained for one and thesame constellation of transmitters. In an article by Andreas Gamst "Aresource allocation technique for FDMA systems" published in AltaFrequenza, Vol. LVII-N.2 February-March 1988, a technique for resourceallocation in a mobile radio system is described. The channelrequirement and exclusion matrix is obtained by means of a data program(GRAND) which utilizes topographic data, predictions for wavepropagation and a statistical model for station hand-over. For acellular system, the lower limit for the requirement of the number offrequency channels is calculated. A heuristic allocating algorithm whichprovides a frequency allocation plan is iterated and the number offrequencies calculated for each frequency plan. The allocating algorithmincludes a random control and the number of frequencies therefore doesnot become the same with each iteration. If the number of frequencies ina frequency plan is less than or equal to the calculated lower limit forthe frequency requirement, an acceptable frequency plan has been foundand the iterations are concluded.

BRIEF SUMMARY OF THE INVENTION

The present invention offers a new and improved allocating algorithmwhich on the one hand utilizes figures of merit calculated in amathematical/logical way for forming possible combinations of stationsand on the other hand utilizes a random technique for the selection ofone of these combinations. The invention is specified in greater detailin the subsequent patent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail with reference tothe attached drawings, wherein

FIG. 1 illustrates how a mobile station is exposed to interference froman adjoining base station,

FIG. 2 illustrates how a base is exposed to interference from a mobilestation in the adjoining area,

FIGS. 3-5 are examples of plots of different interference situations

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

It is the object of the invention to effect resource allocation in aradio system. The prerequisites are that there are a number of basestations each with its own coverage area and a frequency band for thesystem with a limited number of channels. There is also a requirementfor the type of C/I interference characteristic which is needed for goodreception and how much interference the receiver tolerates in adjoiningchannels. The field strengths are measured along the relevant routes inthe respective coverage areas. From the measured values thecross-interference matrices are calculated which indicate theinterference characteristic between transmitters by means of numericvalues. From the cross-interference matrices is calculated an exclusionmatrix which indicates in symbolic form the interference characteristicsbetween transmitters, and especially base stations. The channelallocation is carried out with the aid of the exclusion matrix.

Using a specially calibrated receiver equipment, the received power fromall base stations is measured on the relevant traffic routes in thegeographic area which is covered by the mobile radio system. For thesemeasurements, the measured field strengths provide mean values oversections of 20 m (approximately 30 wavelengths) and each section is tiedto a coordinate designation. The field strength values are representedin the measured material of the received signal power in dBm. Themeasurements are not as comprehensive as they could be since, in thesame process, field strengths can be registered for up to 12 basestations at a time. It is quite possible to make all necessarymeasurements for a cell including coverage and interference range in onenight. This type of measurement has already been successfully performedin the Stockholm area.

The measurements provide knowledge about what potential power a receiverin a mobile set will receive from different cells whilst the mobile islocated in the geographic area. It is also easy to calculate thepotentially received power at an arbitrary base station originating frommobile stations within the coverage area. Consequently the interferencesituation both for mobile stations and base stations is known.

Thus the exclusion matrix provides a systematic description in symbolicform of how different base stations or alternatively mobile stations indifferent coverage areas can be shared with respect to co-channel andadjacent-channel conditions.

The appearance of the matrix is based on which limit values are set forinterference and coverage. It is important to understand that anexclusion matrix certainly contains information on how the channels canbe arranged, but in spite of this is not a quantity which is based onfrequency but only describes the relations between field strengths inthe space.

Since the interferences can be described on the one hand with referenceto the base station receivers and on the other hand with reference tothe receiver of the mobile units there is both an uplinking matrix and adownlinking matrix. (Naturally only the downlinking matrix is used inpaging systems.) If it were so in practice that different channelallocations could be used for uplinking and downlinking, each of thesematrices could be directly used separately for constructing theseallocations after symmetrization. However, it is intended to use thesame allocation in both directions which implies that the allocatingalgorithms are applied to the union of these matrices.

The downlinking situation is shown in FIG. 1. Assuming that all the basestations together with the corresponding service areas are numbered from1 to N. FIG. 1 shows two stations i and J with the associated serviceareas. A mobile station M in the i-th coverage area receives a desiredpower Pi from its own base station and an unwanted interference power Pjfrom base station number J. There is a small difference between the term"service area" and "coverage area". Coverage area here means allmeasured paths which, with respect to a given base station, have asufficiently high received power to allow satisfactory reception. In theservice area there can be points which have not been measured to havegood reception.

The minimum allowable C/I (carrier to interference) noise ratio foracceptable co-channel quality is LP1 and the minimum allowable C/I foracceptable quality for interference in the first adjacent channel is LP2and so forth. For adjacent channel (k-1):a, C/I must be greater thanLPk, k≦M. The noise figure p is defined as the fraction of the coveragearea for which it holds true that

    Pi/pj<LPk

K=1,2, . . . M

M constitutes the number of necessary co-channel and adjacent-channellimit values. The element Pij in a general N-th order cross-interferencematrix is given by the relation

    Pii (LPk)=P

The diagonal elements are set to zero, that is to say

    Pij (LPk)=0 for all i and k.

This cross-interference matrix P refers to the downlinking situation anddescribes which degree of interference the mobile stations are subjectto with respect to the transmitting base stations.

FIG. 2 illustrates the uplinking situation. The figure shows two basestations i and j with associated service areas. In this case the basestation i is exposed to interference Qj from a mobile station Mj in thecoverage area of base station j. The base station i receives a wantedpower Qi from a mobile station Mi in its coverage area. The coverageareas are defined in the same way as before or possibly adjusted for anyimbalance in the power budgets for uplinking and downlinking.

When the mobile station Mj is assumed to pass through the entirecoverage area of base j, an interference power is generated in the basestation i. The interference power at the base station i which fallsbelow y% of the coverage area in j is designated by Qjy. Suitable valuesof y can be 50 or 90. The minimum allowable C/I noise ratio for anacceptable co-channel quality is designated by LQ2 and the minimum C/Ifor an acceptable quality for the first adjacent channel is designatedby LQ2 and so forth. For the adjacent channel (k-1):a, C/I must begreater than LQk, k≦M in the same way as before.

The noise figure q is defined as the fraction of the coverage area ofbase i for which it holds true that

    Qi/Qjy<LQk

A general N-th order exclusion matrix is defined by the relation

    Qij (LQk)=q

The diagonal elements are set to zero in the same way as before, that isto say

    Qii (LQk)=0 for all i and k.

In this way, a cross-interference matrix for each k=1, 2 . . . M isshown. This cross-interference matrix Q relates to the uplinkingsituation and describes which degree of interference the receivers inthe base stations are subject to with respect to transmitting mobilestations.

Alternatively, the uplinking matrix can be calculated in the followingway. When the mobile station Mj in FIG. 2 passes through the entirecoverage area of base j, a noise power is generated in base i. The noisepower varies with the instantaneous position of the interfering mobilestation and its different noise power results can be characterizedstatistically by means of a distribution function.

a) The distribution function is calculated with a starting point frommeasured field strength values. The interference values are generated byperforming a randomization according to the said distribution which canbe implemented, for example, by allowing all interference results to berepresented in table form and uniformly pointing out all numericalvalues in the table.

Assuming that a mobile station Mi passes through the coverage area i andin doing so experiences the coverage field strength Qi and a randomizedinterference field strength Qj at a given point in the coverage area.The noise figure q (q being the element Qij (Lqk) in thecross-interference matrix for uplinking) is defined as the fraction ofthe coverage area of base i for which it holds true that

    Qi/QJ<LQk.

Due to the fact that the interference field strength QJ is randomized,the ratio Qi/QJ is made a stochastic variable. The consequence is that qis also a stochastic variable which assumes new values each time thecalculation is carried out. It is found in practice that the q valuescalculated in this way are assembled well around their mean value andthat an individual result can be considered as representative. If it isnot considered satisfactory, there is always the possibility ofestimating the mean value of q by simulating the effect of theinterfering mobile station several times in the way described above.

b) The distribution function is approximated by means of alogarithmically normal distribution. It is well known in the literaturethat interference field strengths originating from mobile stationssituated at the same distance from the base have an almostlogarithmically normal distribution. This applies also with goodapproximation to interference field strengths at a base from mobilestations in an adjoining coverage area. The log-normal distribution iscompletely determined by the mean value and spread, which parameters canbe easily calculated from the given measured interference fieldstrengths. Compared with case a), it is thus not the distributionfunction which is calculated but only the mean value and spread for thetrue distribution of interference values. The true distribution isfurther approximated with a logarithmically normal distribution. Themedian for the true logarithmated interference field strengths can bevery well used as mean value in the lognormal distribution. Thesimulated interference powers are generated with the aid of a generatorfor normally distributed numerical values and with knowledge of the meanvalue and spread as above. The elements Qij (LQk) in thecross-interference matrix are calculated analogously to what has beensaid in a) above.

The power values Q in the base stations from the transmitting mobilestations are directly relateable to the power values P from thetransmitting base stations due to the fact that the transmission lossesbetween base and mobile station do not depend on the transmittingdirection. Since the P-value is only obtained by measuring wavepropagation data, this also applies to Q values.

To calculate the frequency compatibility, each coverage area must bestudied with respect to all the other coverage areas. This must be donefor all the threshold values corresponding to co-channel interference oradjacent-channel interference. It implies that all elements in allrelevant cross-interference matrices must be calculated. Whilstprocessing measurement data, it is generally unavoidable to calculateall elements in the downlinking and uplinking matrices for thecross-interferences with respect to at least the co-channel case and thecase of noise in the first adjacent channel, that is to say twocross-interference matrices must be calculated for downlinking and twofor uplinking.

To make an allocation program which operates with cross-interferencematrices as starting point works well but it is easier to edit and makechanges in the matrices, which is necessary if the matrices are to beused in practice, if they have a simpler form with not so fully detailedinformation. This is the reason for going over to a simplifiedrepresentation which is here called 10 exclusion matrix. In the matrix adistinction is made between at least three different degrees ofinterference which are usually designated, X or A in ascending degreesof difficulty. The symbol "." designates an interference which isnegligible. The diagonal has elements which are usually designated by 0and which indicate which base station the row or column in the matrixrelates to, for example 0 in row number J means that all interferencesrelate to the coverage area of base station number j.

From the cross-interferences for downlinking with the elements Pij(LPk), for example, the corresponding exclusion matrix can be formed inthe following way:

Assuming that the limit values for the same co-channel and the firstadjacent channel are the only relevant ones, which implies that thereare two cross-interference matrices Pij (LP1) and Pij (LP2). If theexclusion matrix is designated uij and the limit value of the degree ofinterference is px in both cases, the matrix elements uij are obtainedin the following way

uij="0"; i=j

uij="A"; Pij (LP2)>px

uij="X"; Pij (LP1)>px

uij="."; Pij (LP1)≦px

The matrix elements vij in the uplinking matrix are formed incorresponding manner by using the cross-interference matrices Qij (LQ2)and Qij (LQ1) and corresponding limit values for the degree ofinterference py.

                  TABLE 3a                                                        ______________________________________                                        0.00     0.01          0.01   0.06                                            0.00     0.00          0.00   0.00                                            0.00     0.00          0.00   0.00                                            0.07     0.01          0.00   0.00                                            ______________________________________                                    

                  TABLE 3b                                                        ______________________________________                                        0.00     0.04          0.02   0.20                                            0.06     0.00          0.00   0.00                                            0.00     0.00          0.00   0.00                                            0.33     0.03          0.00   0.00                                            ______________________________________                                    

Table 3a shows an example of a cross-interference matrix Pij (LP2) andTable 3b shows a cross-interference matrix Pij (LP1). It holds true thatPij (LP2)≦Pij (LP1); for the rest, there is no connection between thematrices, neither are the matrices symmetric.

By using the above methods, an exclusion matrix can be calculated fromthe cross-interference matrices in the above tables for px=0.05. Theexclusion matrix is shown in Table 4a,

                  TABLE 4a                                                        ______________________________________                                                     O..A                                                                          XO..                                                                          ..O.                                                                          A..O                                                             ______________________________________                                    

The symbols ".", "X" and "A" correspond respond to interferences ofincreasing degree of difficulty. An interference corresponding to "."can be accepted as a co-channel interference. The symbol "0" indicatesthe coverage area to which the interferences in the same column relate.The matrix according to Table 4a can be interpreted as follows. A mobilestation with coverage from base station 1 cannot share a channel forreception with a mobile station in coverage areas 2 and 4. However, itcan share a channel with a mobile station in coverage area 3. It cannotuse an adjacent channel to a channel used by a mobile station incoverage area 4. On the other hand, a mobile station with coverage frombase station 2 can share a channel for reception with a mobile stationin coverage area 1. A mobile station in coverage area 2 is thus notexposed to interferences from base station 1 but a mobile station incoverage area 1 is exposed to interferences from base station 2.Naturally, this implies in practice that the base stations 1 and 2cannot use the same transmitting frequency. The consequence is that onlysymmetrical exclusion matrices have any practical value.

The exclusion matrix is therefore symmetrized by allowing matrixelements which represent the stronger degree of disturbance to beapplicable. If the matrix in Table 4a is symmetrized, the matrix in thefollowing Table 4b is obtained which in this case represents thedownlinking

                  TABLE 4b                                                        ______________________________________                                                    OX.A                                                                          XO..                                                                          ..O.                                                                          A..O --;                                                          ______________________________________                                    

An example of an uplinking matrix is given in Table 5.

                  TABLE 5                                                         ______________________________________                                                   1         2        3      4                                        ______________________________________                                        1          O         X        X      A                                        2          X         O        .      .                                        3          X         .        O      .                                        4          A         .        .      O                                        ______________________________________                                         According to this matrix, the base station 1 cannot share a channel with     base stations 2, 3 and 4 nor can it have an adjacent channel to base     station 4 in receiving mode. Base station 2 is exposed to negligible     interference from mobile stations in the coverage areas of base station 3     and 4 and can therefore share a channel with these base stations, and so     forth.

As mentioned earlier, it is desirable to make the same channelallocations in the uplinking and downlinking directions. To produce amatrix which can be used for forming the same allocation in bothdirections, the union of matrices U and V is defined. The union of twomatrices is defined as the matrix with the union of correspondingelements in each matrix. The symbol for the union of two matrix elementsis the symbol for the element which represents the strongerinterference.

Table 6 shows the union of the matrices in Table 4b and 5

                  TABLE 6                                                         ______________________________________                                                   1         2        3      4                                        ______________________________________                                        1          O         X        X      A                                        2          X         O        .      .                                        3          X         .        O      .                                        4          A         .        .      O                                        ______________________________________                                    

exclusion matrix thus combined by combining its rows is used. If acertain control is required to the effect that small, individuallypermissible noise contributions do not add up too much during theprocess of allocation, for example, a further two levels "Y" and "Z" canbe introduced in the following way. For the downlinking matrix, thematrix element is set as follows:

uij="O"; i=j

uij="A"; Pij (LP2)>px

uij="X"; Pij (LP1)>px

uij="Y"; px/2 <Pij (LP1)≦px

uij="Z"; px/4 <Pij (LP1)≦px/2

uij="."; Pij (LP1)≦px/4

where px=limit value for the degree of interference in the same way asbefore. The exclusion matrix for the uplinking situation can be formedcorrespondingly in certain cases.

As mentioned before, the allocation is carried out by combining the rowsin the exclusion matrix which is thus compressed. When the matrix cannotbe compressed any further, a channel is allocated to each row in thematrix obtained.

There are many known variants of the algebraic procedure itself. Thesevariants include different principles concerning which row should beused as a starting point in the matrix, which alternative should beselected from a large number of largely equivalent values in a givensituation, different types of weighting in the calculation of the figureof merit controlling the procedure and so forth. There is noall-embracing theory on how to manage, but the procedures are heuristicand have been tested with computer simulations on random configurationsof transmitters. These algorithms are certainly tested on randomtransmitter locations but the procedures themselves are deterministic,which means that each time the algorithm is run, exactly the sameallocation is obtained for the same constellation of transmitters.

According to the invention, randomly controlled algorithms are used. Incases where a number of alternative actions happen to be almostequivalent, which is determined by calculating heuristic figures ofmerit, a randomization is carried out for selecting the continued courseof the procedure.

The Applicant has implemented an allocation procedure specified by Haleon computer and it has been possible to make certain comparisons formobile radio applications in Stockholm. It is thought that the randomlycontrolled allocation procedure can provide slightly lessspectrum-effective allocations on average than the allocation obtainedby means of the deterministic procedure. However, this is balanced bythe fact that from the great number of allocations obtained by means ofthe randomly controlled procedure, single allocations can be obtainedwhich are extremely good. A number of different allocations which solvethe same problem provide the operator with more information than asingle allocation which solves the current problem. Furthermore, certainsecondary conditions which are difficult to formulate mathematically canbe satisfied by a suitable selection of the required allocation from anumber of allocations.

EXAMPLE

The invention is illustrated below by means of an example. 48 stationsare placed out beforehand in the Stockholm area. The necessary fieldstrengths have been measured or calculated so that the exclusion matrixcan be formed as above. To simplify the discussion, it is assumed thatno channels are preallocated, that is to say the allocation is carriedout without boundary conditions.

1. Starting from a number of base stations, see Table 7, an exclusionmatrix is formed, see Table 8.

                  TABLE 7                                                         ______________________________________                                        NR      CHANNEL        NAME                                                   ______________________________________                                         1.     0.             AARSTA                                                  2.     0.             BOTKYRKA                                                3.     0.             HALLONBERGEN                                            4.     0.             HUDDINGE                                                5.     0.             HOTORGET.sub.-- N                                       6.     0.             HOTORGET.sub.-- NO                                      7.     0.             HOTORGET.sub.-- NV                                      8.     0.             HOTORGET.sub.-- S                                       9.     0.             HOTORGET.sub.-- SO                                     10.     0.             HOTORGET.sub.-- SV                                     11.     0.             ODENPLAN                                               12.     0.             ROSENLUND                                              13.     0.             RYDHOLM                                                14.     0.             SALTSJOBADEN                                           15.     0.             SANDHAMN                                               16.     0.             SKATTEHUSET                                            17.     0.             SKAMOLMEN                                              18.     0.             SOLBERGA                                               19.     0.             SOLLENTUNA                                             20.     0.             STADION                                                21.     0.             STADSHAGEN                                             22.     0.             STAVSNAS                                               23.     0.             STENHAMRA                                              24.     0.             STJARNHOV                                              25.     0.             STRANGNAS                                              26.     0.             SUNDBYBERG                                             27.     0.             SV.HOGARNA                                             28.     0.             SATRA                                                  29.     0.             SODERTAWE.sub.-- C                                     30.     0.             TELESKOLAN                                             31.     0.             TOMTEBODA                                              32.     0.             TORO                                                   33.     0.             TUMBA                                                  34.     0.             TUNGELSTA                                              35.     0.             UPPLANDS.sub.-- VASBY                                  36.     0.             UPPSALA.sub.-- N                                       37.     0.             UPPSALA.sub.-- O                                       38.     0.             UPPSALA.sub.-- S                                       39.     0.             UPPSALA.sub.-- V                                       40.     0.             VALLENCUNA                                             41.     0.             VAXHOLM                                                42.     0.             VEDYXA                                                 43.     0.             VALLINGBY                                              44.     0.             VASTERÅS                                           45.     0.             ÅRSTADAL                                           46.     0.             ALTA                                                   47.     0.             OSTERMALM                                              48.     0.             OSTERSKAR                                              ______________________________________                                        0.0000  1.   O..X...X...X...X.X..X......X.X..............XX..                 0.0000  2.   .O.X............XX....XX...XX..XXX..............                 0.0000  3.   ..O...X...X.X.....X.X....X.X..X...X.......X.....                 0.0000  4.   XX.O............XX.........X....XX..............                 0.0000  5.   ....OXXXXXX....X...XX.........................X.                 0.0000  6.   ....OXXXXXX....X...XX.........................X.                 0.0000  7.   ..X.XXOXXXX....X....X....X...XX.................                 0.0000  8.   X...XXXOXXXX...X....X........X..............XXX.                 0.0000  9.   ....XXXXOXX....X...XX........................XX.                 0.0000 10.   ....XXXXXOXX...X....X......X.XX.............X...                 0.0000 11.   ..X.XXXXXXO........X.....X....X...............X.                 0.0000 12.   X......X.X.O...X.X..X......X.X..............X...                 0.0000 13.   ..X.........O.....X...............X....X.X......                 0.0000 14.   .............OXX.....X....X....X........X....X..                 0.0000 15.   .............XO......X....X... X........X......X                 0.0000 16.   X...XXXXXX.X.X.O.X..X..........X............XXX.                 0.0000 17.   .X.X............OX....X..X.X....X...............                 0.0000 18.   XX.X.......X...XXO.........X.X..XX..........X...                 0.0000 20.   ....XX..X.X........O....................X.....X.                 0.0000 21.   X.X.XXXXXX.X...X....O....X.X.XX...........X.X...                 0.0000 22.   .............XX......O....X....X.X......X....X.X                 0.0000 24.   .X....................XOX...X..X................                 0.0000 25.   ......................XXO..................X....                 0.0000 26.   ..X...X...X.....X.X.X.X..O.X..X...........X.....                 0.0000 27.   .............XX......X....O....X........X.......                 0.0000 28.   XXXX.....X.X....XX..X.X..X.O.X............X.X...                 0.0000 29.   .X....................XX....O...XX..............                 0.0000 30.   X.....XX.X.X...X.X..X......X.O..............X...                 0.0000 31.   ..X...X..XX.........X....X....O.................                 0.0000 32.   .X...........XX......X.X..X....OXX..............                 0.0000 33.   .X.X............XX..........X..XOX...........X..                 0.0000 34.   .X.X.............X...X......X..XXO...........X..                 0.0000 35.   ..X.........X.....X...............O....XXX.....X                 0.0000 36.   ...................................OXXX..X......                 0.0000 37.   ...................................XOXX..X......                 0.0000 38.   ...................................XXOX..X......                 0.0000 39.   ...................................XXXO..X......                 0.0000 40.   ............X.....X...............X....OXX.....X                 0.0000 41.   .............XX....X.X....X.......X....XO......X                 0.0000 42.   ............X.....................XXXXXX.O......                 0.0000 43.   ..X...............X.X....X.X..............O.....                 0.0000 44.   ........................X..................O....                 0.0000 45.   X......X.X.X...X.X..X......X.X..............O...                 0.0000 46.   X......XX....X.X.....X..........XX...........O..                 0.0000 47.   ....XX.XX.X....X...X..........................O.                 ______________________________________                                         The exclusion matrix is symmetrized.

2. All rows in the matrix are allocated a figure of merit. The figure ofmerit is defined most simply with the aid of the concept of scalarproduct. For one row, the figure of merit is obtained by considering therow as a vector where the symbols ".", "X", "O" and "A" have , differentintegral-number weight and thereafter form the scalar product of thevector with themselves. Let the weights be zero for "." and "O" and asuitable integral-number value, for example 1, for "X" and "A". Incertain connections, "A" can be allowed to have a higher integral-numberweight, for example 2 or 3. If the integral-number weights are equal to1, the figure of merit represents the sum of the number "X" and "A".

The figure of merit for a pair of vectors generally represents thescalar product between corresponding integral-number vectors. If theweights of "X" and "A" are equal to 1, the figure of merit representsthe number of common "X" and "A". A high value of the figure of meritindicates in this case a geographic closeness and this can beinterpreted so that a good value of the figure of merit tends toconcentrate compatible base stations in the area. This is a differentway of saying that short repetition intervals are aimed for, which, inturn is a prerequisite for good frequency economy.

The exclusion matrix is not necessarily to be symmetrized for theallocating algorithms to function. The figures of merit become slightlydifferent which entails that the algorithms have different priorities inthe random value. An advantage with a symmetrical matrix is that, onaverage, it needs fewer operations to carry out the allocations.

3. Selection of a first row in the matrix. This can be carried out bycalculating the figure of merit for all rows and sorting the rows bydecreasing figure of merit. Random selection of the row which representsthe starting row from, for example, the 10 best rows.

4. When the starting row is determined, the rest of the rows arecalculated which are compatible with the starting row. Sorting of theserows by figure of merit relative to the starting row by decreasingfigure of merit. Random selection of the row which will be "added" tothe starting row (the union is formed) from a fixed number of the bestrows. After each addition, a new amount of compatible candidates iscalculated and the procedure is repeated until there are no longer anycompatible rows to be added.

5. Selection of a new starting row from the "free" number of rows in thesame way as in 3. This row now represents the next channel in theallocation procedure. The rows which are compatible with this row arenow calculated in the same way as in item 4.

6. The procedure according to item 5 is repeated again until no rowsremain in the free set. A so-called allocation matrix has now beencreated according to Table 9.

                                      TABLE 9                                     __________________________________________________________________________    1.0                                                                             XXXOXXXXXXXXXXXXXXOXOXOXXXXXXXXOXXXXXXXXOOXOXOOX                            2.0                                                                             XXOXXXXXOXXXXOXXOXXXXXXXOXXXOXXXXXXXXOXXXXXXOXXO                            3.0                                                                             XXXXXXXXXXXXXXXOXXXOXXXOXXOOXXOXXOXOXXXOXXX.XXXX                            4.0                                                                             XOXXOXXXXXXXXXXXXXXXXOXX.OXXXOXXXXOXOXXXXXX.XXXX                            5.0                                                                             OXXXXXOXXXXXOXOXXXX.XX...XXXXXXXOXXXXXOXXXO.XX.X                            6.0                                                                             X...XOXXXXXO...X.X.XX......X.X..............X.X.                            7.0                                                                             XX.XXXXOXXXX...XXO..X......X.X..XX..........XXX.                            8.0                                                                             ..X.XXXXXXO........X.....X....X...............X.                            9.0                                                                             ....XXXXXOXX...X....X......X.XX.............X...                            __________________________________________________________________________    ANTAL KANALER: 9                                                                                1.0                                                                             4  19                                                                              21                                                                              23                                                                              32                                                                              41                                                                              42                                                                              44                                                                              46                                                                              47                                                       2.0                                                                             3   9                                                                              14                                                                              17                                                                              25                                                                              29                                                                              38                                                                              45                                                                              48                                                         3.0                                                                             16 20                                                                              24                                                                              27                                                                              28                                                                              31                                                                              34                                                                              36                                                                              40                                                         4.0                                                                             2   5                                                                              22                                                                              26                                                                              30                                                                              35                                                                              37                                                             5.0                                                                             1   7                                                                              13                                                                              15                                                                              33                                                                              39                                                                              43                                                             6.0                                                                             6  12                                                                       7.0                                                                             8  18                                                                       8.0                                                                             11                                                                          9.0                                                                             10                                                        __________________________________________________________________________

The upper part of the table shows the nine compressed rows which remainof the exclusion matrix according to Table 8. Each row corresponds to apotential channel and the sign 0 marks a station which is located in thechannel. The lower part of Figure 9 contains the same information but,instead, for each 0 the column number is given. Thus, station numbers 4,19, 21 and so forth are found in channel 1. In Table 10 the stations arelisted in numerical order in a table like Table 7.

                  TABLE 10                                                        ______________________________________                                        NR      CHANNEL        NAME                                                   ______________________________________                                         1.     5.             AARSTA                                                  2.     4.             BOTKYRKA                                                3.     2.             HALLONBERGEN                                            4.     1.             HUDDINGE                                                5.     4.             HOTORGET.sub.-- N                                       6.     6.             HOTORGET.sub.-- NO                                      7.     5.             HOTORGET.sub.-- NV                                      8.     7.             HOTORGET.sub.-- S                                       9.     2.             HOTORGET.sub.-- SO                                     10.     9.             HOTORGET.sub.-- SV                                     11.     8.             ODENPLAN                                               12.     6.             ROSENLUND                                              13.     5.             RYDHOLM                                                14.     2.             SALTSJOBADEN                                           15.     5.             SANDHAMN                                               16.     3.             SKATTEHUSET                                            17.     2.             SKAMOLMEN                                              18.     7.             SOLBERGA                                               19.     1.             SOLLENTUNA                                             20.     3.             STADION                                                21.     1.             STADSHAGEN                                             22.     4.             STAVSNAS                                               23.     1.             STENHAMRA                                              24.     3.             STJARNHOV                                              25.     2.             STRANGNAS                                              26.     4.             SUNDBYBERG                                             27.     3.             SV.HOGARNA                                             28.     3.             SATRA                                                  29.     2.             SODERTAWE.sub.-- C                                     30.     4.             TELESKOLAN                                             31.     3.             TOMTEBODA                                              32.     1.             TORO                                                   33.     5.             TUMBA                                                  34.     3.             TUNGELSTA                                              35.     4.             UPPLANDS.sub.-- VASBY                                  36.     3.             UPPSALA.sub.-- N                                       37.     4.             UPPSALA.sub.-- O                                       38.     2.             UPPSALA.sub.-- S                                       39.     5.             UPPSALA.sub.-- V                                       40.     3.             VALLENTUNA                                             41.     1.             VAXHOLM                                                42.     1.             VEDYXA                                                 43.     5.             VALLINGBY                                              44.     1.             VASTERÅS                                           45.     2.             ÅRSTADAL                                           46.     1.             ALTA                                                   47.     1.             OSTERMALM                                              48.     2.             OSTERSKAR                                              ______________________________________                                    

The above procedure is exemplified in the concluding table in Table 11which is a table of a random selection of compatible rows.

                  TABLE 11                                                        ______________________________________                                        48    0      47    0     46  0     45  0     44  0                            43    0      42    0     41  0     40  0     39  0                            38    0      37    0     36  0     35  0     34  0                            33    0      32    0     31  0     30  0     29  0                            28    0      27    0     26  0     25  0     24  0                            23    0      22    0     21  0     20  0     19  0                            18    0      17    0     16  0     15  0     14  0                            13    0      12    0     11  0     10  0      9  0                             8    0       7    0      6  0      5  0      4  0                             3    0       2    0      1  0                                                KANAL 1: 46                                                                   21    4      32    4     18  4      4  3     47  3                            45    3      10    3      7  3      6  3      5  3                            30    3      12    3     15  2     29  2      2  2                            27    2      41    2     11  2     48  1     17  1                            28    1      20    1     44  0     43  0     42  0                            40    0      39    0     38  0     37  0     36  0                            35    0      31    0     26  0     25  0     24  0                            23    0      19    0     13  0      3  0                                      KANAL 1: 21                                                                   11    9      18    8     47  5     32  4      4  4                            19    3      17    3      2  3     20  3     15  2                            29    2      27    2     41  2     23  2     48  1                            13    1      35    1     44  0     42  0     40  0                            39    0      38    0     37  0     36  0     25  0                            24    0                                                                       KANAL 1: 32                                                                   18    9      11    9      4  5     47  5     29  4                            17    4      23    4     41  4     20  3     19  3                            48    2      13    1     35  1     25  1     44  0                            42    0      40    0     39  0     38  0     37  0                            36    0                                                                       KANAL 1: 4                                                                    11    9      23    5     47  5     29  4      41 4                            20    3      19    3     48  2     13  1     35  1                            25    1      44    0     42  0     40  0     39  0                            38    0      37    0     36  0                                                KANAL 1: 23                                                                   11    9      47    5     41  4     19  3     20  3                            48    2      44    1     35  1     13  1     42  0                            40    0      39    0     38  0     37  0     36  0                            KANAL 1: 47                                                                   41    5      19    3     48  2     44  1     35  1                            13    1      42    0     40  0     39  0     38  0                            37    0      36    0                                                          KANAL 1: 41                                                                   19    5      13    3     42  2     44  1     39  0                            38    0      37    0     36  0                                                KANAL 1: 42                                                                   19    6      44    1                                                          KANAL 1: 19                                                                   48    0      45    0     43  0     40  0     39  0                            38    0      37    0     36  0     35  0     34  0                            33    0      31    0     30  0     29  0     28  0                            27    0      26    0     25  0     24  0     22  0                            20    0      18    0     17  0     16  0     15  0                            14    0      13    0     12  0     11  0     10  0                             9    0       8    0      7  0      6  0      5  0                             3    0       2    0      1  0                                                KANAL 2: 45                                                                    7    5       6    4      5  4      9  4     26  2                            43    2      17    2     11  2     31  2      3  2                             2    2      14    1     34  1     33  1     48  0                            40    0      39    0     38  0     37  0     36  0                            35    0      29    0     27  0     25  0     24  0                            22    0      20    0     15  0     13  0                                      KANAL 2: 9                                                                     3    4      31    4     26  4     14  2     43  2                            17    2      34    2     33  2      2  2     22  1                            48    0      40    0     39  0     38  0     37  0                            36    0      35    0     29  0     27  0     25  0                            24    0      15    0     13  0                                                KANAL 2: 14                                                                   34    4      26    4     31  4      3  4     48  3                             2    3      33    3     43  2     17  2     40  1                            35    1      24    1     39  0     38  0     37  0                            36    0      29    0     25  0     13  0                                      KANAL 2: 3                                                                    48    4      40    4     34  4     17  3     33  3                             2    3      24    1     39  0     38  0     37  0                            36    0      29    0     25  0                                                KANAL 2: 48                                                                   34    4      17    3     33  3      2  3     24  1                            39    0      38    0     37  0     36  0     29  0                            25    0                                                                       KANAL 2: 17                                                                   34    7      29     3    24  3     25  1     39  0                            38    0      37    0     36  0                                                KANAL 2: 25                                                                   34    7      29    4     39  0     38  0     37  0                            36    0                                                                       KANAL 2: 29                                                                   39    0      38    0     37  0     36  0                                      KANAL 2: 28                                                                   43    0      40    0     39  0     37  0     36  0                            35    0      34    0     33  0     31  0     30  0                            28    0      27    0     26  0     24  0     22  0                            20    0      18    0     16  0     15  0     13  0                            12    0      11    0     10  0      8  0      7  0                             6    0       5    0      2  0      1  0                                      KANAL 3: 36                                                                   13    1      40    1     35  1     43  0     34  0                            33    0      31    0     30  0     28  0     27  0                            26    0      24    0     22  0     20  0     18  0                            16    0      15    0     12  0     11  0     10  0                             8    0       7    0      6  0      5  0      2  0                             1    0                                                                       KANAL 3: 34                                                                   24    3      1     3     28  3     16  2     15  2                            27    2      8     1     40  1     35  1     13  1                            30    1      12    1     43  0     31  0     26  0                            20    0      11    0     10  0      7  0      6  0                             5    0                                                                       KANAL 3: 16                                                                   28    9      11    7     20  4     27  3     15  3                            24    3      31    3     26  2     43  1     40  1                            35    1      13    1                                                          KANAL 3: 20                                                                   28    9      31    4     27  4     15  4     24  3                            26    3      35    2     40  2     43  1     13  1                            KANAL 3: 24                                                                   28    10                                                                      7                  4     26  4     15  4     31  4                            35    2      40    2     43  1     13  1                                      KANAL 3: 28                                                                   31    6      27    4     15  4     35  3     40  2                            13    2                                                                       KANAL 3: 31                                                                   27    4      15    4     35  3     40  2     13  2                            KANAL 3: 40                                                                   15    4      27    4                                                          KANAL 3: 27                                                                   43    9      39    0     37  0     35  0     33  0                            30    0      26    0     22  0     18  0     15  0                            13    0      12    0     11  0     10  0      8  0                             7    0       6    0      5  0      2  0      1  0                            KANAL 4: 37                                                                   13    1      35    1     43  0     33  0     30  0                            26    0      22    0     18  0     15  0     12  0                            11    0      10    0      8  0      7  0      6  0                             5    0       2    0      1  0                                                KANAL 4: 30                                                                    6    5       5    5     11  3     26  3     43  2                             2    2      35    1     33  1     13  1     22  0                            15    0                                                                       KANAL 4: 5                                                                    26    4      43    2      2  2     35  1     33  1                            13    1      22    0     15  0                                                KANAL 4: 35                                                                   26    6      43    4      2  2     22  2     15  2                            33    1                                                                       KANAL 4: 22                                                                   26    6      43    4     33  4      2  4                                      KANAL 4: 26                                                                    2    6      33    5                                                          KANAL 4: 2                                                                    43    0      39    0     33  0      18 0     15  0                            13    0      12    0     11  0     10  0      8  0                             7    0       6    0      1  0                                                KANAL 4: 43                                                                    7    3      12    2     11  2     10  2      1  2                            13    2       6    1      8  1     18  1     39  0                            33    0      15    0                                                          KANAL 5: 1                                                                    10    7       7    6      6  3     33  3     11  3                            13    2      39    0     15  0                                                KANAL 5: 7                                                                    33    3      13    2     39  0     15  0                                      KANAL 5: 15                                                                   33    4      13    2     39  0                                                KANAL 5: 13                                                                   33    4      39    1                                                          KANAL 5: 33                                                                   18    0      12    0     11  0     10  0       8 0                             6    0                                                                       KANAL 6: 12                                                                    6    4      11    2                                                          KANAL 6: 6                                                                    18    0      11    0     10  0      8  0                                      KANAL 7: 8                                                                    18    5                                                                       KANAL 7: 18                                                                   11    0      10    0                                                          KANAL 8: 11                                                                   10    0                                                                       KANAL 9: 10                                                                   ______________________________________                                         For this special case, all rows in the exclusion matrix have been     allocated the same figure of merit even though the number "X" differs     between different rows. The pair of numbers in the table shows on the one     hand the row number and on the other hand the figure of merit in a     selection of corresponding rows. The very first part-table has at the top     the pair of numbers representing all conceivable 48 rows and all have the     same figure of merit defined as zero in this particular case. It is     therefore immaterial which starting row is used and in this case row     number 46 has been randomly selected. In the next part-table, all rows are     shown which are compatible with row no. 46 and the figures of merit of     these rows. These figures of merit are calculated as scalar products as     above. The figure of merit 4 in (21 4) thus represents the number of     common "X" in rows 46 and 21. Among the five rows which have the highest     figure of merit row 21 is randomly selected, which is thus added to row     46. In continuation, rows 32, 4, 23, 47, 41, 42, 19 and 44 are also added.     These compatible rows represent the same number of base stations with     associated coverage areas and all these base stations can use the same     channel 1 for transmitting and receiving (channel 1 is located both in the     uplinking band and the downlinking band).

When all rows corresponding to channel 1 are added, a new starting rowis randomly selected in this special case from the free set, by means ofwhich channel 45 is obtained.

The above procedure is repeated and randomizations cause the rows 45, 9,14, 3, 48, 17, 25, 29 and 38 to be arranged together to form a singlerow which corresponds to channel 2.

When a new starting row has been selected 9 times, no rows are left inthe free set and no further rows exists which is compatible with row 10.The allocation procedure is thereby concluded.

With channel allocation in the microcell system in, for example,Stockholm, channel allocations in a surrounding area of Stockholm mustbe taken into consideration, that is to say the allocation is madetowards a certain boundary. The boundary can also include arbitrary basestations in Stockholm which for one or other reason must stay fixed withrespect to channel. This condition is only controlled by means of thealgebraic allocation procedure by combining all rows in the exclusionmatrix which correspond to one and the same channel. With the continuedallocation, the row operations act as allocation restriction with thegiven channel spacing.

According to the invention, a control of the total degree ofinterference is made possible. According to what was said before, anallocating algorithm involves the purely algebraic execution of a numberof row operations in a cross-interference matrix or symmetrizedexclusion matrix. Small matrix element values in cross-interferencematrices are with good approximation additive when rows are combined.This is due to the fact that the interference contributions fromdifferent transmitters in the same coverage area are independent of oneanother if the coverage area exposed to the interference does notconstitute a significant part of the whole coverage. If the informationfrom the cross-reference matrices for uplinks and downlinks isaccessible with the allocation procedure, the resultant incidentinterference relating to the interference characteristics in differentcoverage areas can be sufficiently controlled during the allocationprocess by adding corresponding elements in the cross-interferencematrices. If during this process a limit value is exceeded, this is afurther restriction on the combining of rows in the exclusion matrix. Anexample of a very simple implementation of this principle is theintroduction of levels "Y" and "Z" into the exclusion matrix as above.

If it is noticed that the traffic demand of a base station increasesuntil it doubles, measures can be taken against this by copying the itemfor this base station in the exclusion matrix one more time with the aidof a text editor. A specially developed handling program is used forrenumbering all items with respect to the additional item introduced,after which the allocating algorithm is repeated with the new item.

An interference degree B can also be included in the exclusion matrixwhich implies that the interference is not negligible in the secondadjacent channel. Naturally, this implies a further restriction on thecombining of rows. The symbol B will not be found in the same column inless than or equal to two rows from the symbol 0 in a current row.Figure 6 shows an example of the final allocating matrix. There musttherefore be two rows between the symbols 0 and B in the same column,see, for example, rows 3 and 6.

A further aid to the resource allocation is a plotting program whichcreates plots of the interference situation. This is because theelements in an exclusion matrix belong to one of the following threeclasses:

1. Obvious non-exclusions, for example between cells at a very longdistance from one another. It is sufficient to calculate that thecoverage areas do not overlap one another, that is to say a trivialcalculation.

2. Obvious exclusions between, for example, cells which are groupedtogether, that is to say cells which share the same mast or antenna.Collective groupings are easily found by comparing the coordinates ofthe stations.

3. Uncertain pairs of cells where it is difficult to decide whetherthere is an exclusion or not. The number of uncertain pairs is a muchlower number than the number of all cell pairs.

When designing an exclusion matrix, only the elements in thecross-interference matrices which relate to uncertain cell pairs must becalculated, strictly speaking. This is suitably done with the algorithmswhich have been specified earlier in combination with the plottingprogram which produces plots of downlinks and uplinks for current cellpairs. For the uplink, the Monte-Carlo methods specified in a) and b)are to be preferred. The plotting program calculates the degree ofinterference (the value of the corresponding elements in thecross-interference matrix) and provides a visual image of theinterference situation which provides for extremely accurate planning ofthe cell and its interaction with other cells. The planning can now becarried out not only by taking into account the noise figure but alsowith respect to the total interference pattern and keeping in mindsystem-related aspects such as, for example, hand-over boundaries. It ispossible to vary base station powers in power classes for mobilestations and also to regulate the coverage individually for each cell.This can be done simultaneously both for uplinking and downlinking. Inaddition, it is no longer necessary to be bound to a fixed limit valuefor the noise figure, but the cells can be planned individually withrespect to the unique interference pattern.

For example, if the interferences do not create any problem with normaltraffic loading, these interferences can be considered in these cases asbelonging to the coverage area of another cell. The method is exactingwork but provides a result of the highest quality.

FIGS. 3-5 show plots of the service area of the base station inVallingby with respect to interferences from the coverage area aroundthe base station at Odenplan. The downlinking situation is illustratedin FIG. 13 where the limit value for coverage is -93 dBm. The coverageis represented by plotted line segments, the interferences from Odenplanbeing designated by 0. The degree of interference, that is to say theelement in the cross-interference matrix, is calculated as 0.8%.

FIG. 4 shows a plot for a corresponding situation in the uplink. It isthus a picture of how the mobile stations in the coverage area of thebase station at Odenplan interfere with the base station in Vallingby.The degree of interference is here approximately ten times higher thanin the downlink.

FIG. 5 shows a plot of the uplink situation when the limit value forcoverage is raised to -88 dBm. The coverage area has been slightlyreduced but the interference situation has become acceptable with adegree of interference of approximately 4%.

According to the embodiment of the invention described here, measuredfield strength values have been used to construct the exclusion matrix.However, the invention does not exclude the use of calculated fieldstrength values if these are accessible. The invention is only limitedby the patent claims below.

We claim:
 1. A method for allocating resources in a radio systemcomprising the steps of:providing a plurality of base stations;associating a coverage area for each of said base stations; providing aplurality of mobile stations that can move between or within thecoverage areas; determining the area of interaction between basestations and their coverage areas by measurements; calculating a meritfigure for each of said base stations and placing the merit figures inrows of a matrix; randomly selecting a row of said matrix as a startingrow; determining, from the remaining rows, which rows are compatiblewith the starting row in order to determine the best rows, randomlyselecting a row from the subset of the best rows to be added to thestarting row, and; repeating said calculating, selecting and determiningsteps until there are no longer any compatible rows; choosing a row fromthe remaining rows; and assigning transmitting and receiving frequenciesfor each base station based upon the choosing step.
 2. A method as inclaim 1 wherein the step of determining from the remaining rows furthercomprising the steps of:compressing of said matrix; and repeating saidcompressing step of said matrix until no further compression ispossible.
 3. A method as in claim 2 wherein said selecting stepcomprises:a plurality of random selection techniques.
 4. A method as inclaims 1, 2, or 3 wherein said step of calculating further comprisingthe step of:producing a scalar product between vectors in said matrix.5. A method as in claim 4 wherein said step of determining furthercomprises:representing the interaction by a cross-interference matrixwith elements in the form of numerical values.
 6. A method as in claim 4wherein said step of determining further comprises:representing theinteraction by an exclusion matrix with elements in symbol form.
 7. Amethod as in claim 4 wherein said step of determining furthercomprises:representing the interaction by a cross-interference matrixwith elements in the form of numerical values; and representing theinteraction by an exclusion matrix with elements in symbol form.